System for hydrostatically testing hollow bodies



L. A. LASSMAN July 27, 1954 SYSTEM FOR HYDROSTATICALLY TESTING HOLLOW BODIES 2 Shets-Sheet 1 Filed Feb. 11, 1950 INVENTOR LEOARTHUR LASSMAN Patented July 27, 1954 SYSTEM FOR HYDROSTATICALLY TESTING HOLLOW BODIES Leo Arthur Lassman, Pittsburgh, Pa., assignor to Benjamin Lassman & Son, Pittsburgh, Pa., a

partnership Application February 11, 1950, Serial No. 143,789

11 Claims.

This invention relates to a system for hydrostatically testing hollow bodies, such as metal or ceramic pipes and the like, by means of water or other relatively incompressible fluid. More particularly, this invention relates to means for controlling the application of the sealing and. testing forces in said system within close limits of each other to avoid damaging any hollow body undergoing test substantially irrespective of the diameter, length or wall strength or thickness thereof. Further, this invention relates to the subject-matter of United States patent application Serial No. 53,162, filed October 7, 1948, for System for Hydrostatically Testing Hollow Bodies.

In the testing of hollow bodies in pipe benches and similar devices, it is common at the present time to test at pressures in excess of 2500 lbs. per square inch, a figure which usually heretofore constituted the neighborhood of the upper testing pressure limit. Thus, it is not uncommon at the present time to find testing pressures which go as high as 6000 to 12,000 lbs. per square inch. As the upper testing pressure limit continues to increase in commercial practice, it is evident that more sensitive and closer synchronization between the application of the testing force and the counteracting sealing force exerted at the opening in the ends of the hollow body must be obtained. Further, the sealing force must be held within a close limit relative to the testing force. Otherwise, the hollow body undergoing test may be dangerously strained and may even fail. In addition to the hazard to personnel of such a failure, it may damage the machine and in any event will interfere with production. In a large mill such testing may be a continuous production operation, the consequences of the interruption of which may be quite costly.

The problems thus present especially at higher testing pressures are magnified when during such testing hollow bodies of varying internal diameters or differing wall strengths are processed. In the present tendency toward smaller safety factors in the manufacture of, for example, steel pipe, thin-walled pipe is particularly susceptible to crushing or impairment if oversealing is present during the testing. On the other hand, following the usual attempts heretofore made to closely correlate sealing and testing forces might result in undersealing and failure or" the test operation. In addition, at the higher testing pressures especially hollow bodies in the longer lengths particularly were subject to bowing or til \ respective sealing and testing forces.

5 waving during testing, resulting at least in part from the absence of close correlation of sealing and testing forces. As a consequence, it is common in prior testing benches and the like to pro vide clamps to encircle longer sections and as sure the completion of the testing operation without such bowing.

In this invention sensitive and close correlation within narrow limits is obtained between the Further, by means of this invention the sealing pressure and the testing pressure and the respective rates of application thereof may be so interrelated that prompt and continuous production testing at high pressures may be carried on even though there are frequent changes in the sizes or wall strengths of the hollow bodies undergoing testing.

Other objects and advantages of this invention w ll be apparent from the following description and the drawings, which are illustrative only, in which:

Figure 1 is a plan view, partly in cross section and partly schematic, of an apparatus particularly suitable for use in connection with this invention;

Figure 2 is a view in elevation and partly in cross section of an embodiment of this invention;

Figure 3 is a plan view of certain portions of the control apparatus shown in Figure 2;

Figure 4 is a View in end elevation of the apparatus shown in Figure 2;

Figure 5 is a View partly in cross section taken along line V--V of Figure 2; and

Figure 6 is a View taken along line VI-VI of Figure 2.

General arrangement and operation of test bench Referring to Figure 1 a test specimen in the form of a length of pipe It is placed in position in a test bench ll between a sealing head or platen I2 and a rear sealing head I3. The rear sealing head It is held against rearward movement by tension bars l4. The rear sealing head it may be moved to different positions along the tension bars Hi when the pipe to be accommodated is of a different length than the existing setting of the bench. The sealing platen I2 is connected to a sealing housing It by sealing plungers It and a water ,prefilling tube ii integrai in this embodiment with sealing platen [2. The water prefilling tube I? is slidably mounted in bearings l's'a for axial movement through the sealing housing i5 and concentrically therewith.

On the other side of sealing platen i2 there are two hydraulic positioning cylinders 58 fastened to the tension bars id at the appropriate place for the testing of hollow body IE1. At the rear end of the water prefilling tube ll, there is a water valve is actuated through an air cylinder Ed by an air valve 2|. A low pressure water line lilo. adrnits preflll water to valve is, tube ii and pipe it whenever valve 19 is opened by valve 25. A high pressure water line 22 with water t erein at testing pressure is connected to the rear of valve l9 through a flexible pressure coupling 23. The testing pressure water is admitted to the testing pressure system through a valve 2 3. A line con nection 2% in the high pressure Water line of the testing liquid circuit leads into a testing circuit cylinder 2% whereby synchronization between the testing and sealing pressure s stems is effected.

In the sealing liquid circuit a hydraulic fluid, such as oil is preferably used and is supplied from a tank 27. Such oil flows or is drawn ither through line 28 or 25 and its check valve into a sealing pressure pump 39 which also possesses the features of reversible and variable delivery. Adjustable pressure pump 36 is a conventional type in which shifting the interior or working portions thereof to the left or right or" the vertical center line through the axis of the pump produces discharge, respectively through the right or left port of the pump. The intake in each such case is respectively through the left or right port. The pressure of the pump discharge is selectively controlled in part by a pump control mechanism 32 having certain preadjusted springs therein and operating in conjunction with a synchronization cylinder 28 and an air valve 33.

The positioning cylinders it are double-acting and are operated hydraulically by the oil from pump 33s when a four-way hydraulic valve 3d.- is moved into the proper position. In bringing sealing platen l2 into engagement with pipe W by admitting oil into the rod end of cylinders it through pipe 15, sealing plungers IE are withdrawn from sealing housing i and thereby their cylinders 39 are filled with oil from tank 2! through a pipe 35, valve 36 and pipe 3'! and 38. When valve 33 is shut 01?, valve 34 is then turned to relieve the pressure in cylinders l3 and sealing plungers 16 take up the task of putting the sealing members into presealing engagement with pipe ill at low pressure during the prefilling of pipe it with water. Thereafter plungers it hold sealing platen l2 against the pipe as at a much higher sealing pressure without any excessive or oversealing force against pipe l6 during the testing thereof under testing pressure. Plungers l5 and the bores of the cylinders 39 are made to very close tolerances, eliminating the need for packing and providing capillary lub -ication of the plungers by the oil in th sealing pressure system without excessive loss or leakage of oil around the plungers, Oil which does pals out of the cylinders 39 is collected in chambers 42 for return to tank 21. Cylinders 38 are singleacting by the admission of oil thereto through pipes 43 and. 35 under pressure for presealing and sealing in a closing or sealing engagement direction. Various of the valving and circuit connections to test bench H are more fully disclosed in the aforesaid United States patent application Serial No. 53,162 and are particularly suitable for use in the practice of this invention but no claim is made in this invention to the valving and circuit connections as such described in said application Serial No. 53,162.

In a testing operation on bench ll, front and rear sealing heads 12 and I3 and the positioning cylinders l8 are disposed in proper spaced relation on tension bars 24 to accommodate the succession of hollow bodies It to be tested. At the initiation of such a testing operation the test bench is open with plungers it, tube I! and platen 12 positioned to the left as viewed in Figure 1. Further, the sealing liquid circuit is either under no pressure if pump 3i? has been stopped in neutral position, or it is under the pressure control of certain positioning pressure control springs in r. echanism as will hereinafter be described. The testing liquid circuit is under no pressure inasrnuch as both the high. pressure valve 2 the low pressure valve iii are normally closed at this stage. After placing a hollow body iil between the sealing heads i2 and i3, pneumatic valve 33, if not such position, is turned to admit compressed air to an air cylinder in mechanism 32 to cause pump to discharge its hydraulic liquid into the sealing pressure circuit to close the bench when hydraulic valve 3 is turned to admit such liquid through lines M and 45 to the piston rod end of cylinders l8, thereby moving sealing head l2 into position to clamp hollow body ill between it and sealing head it, as shown in Figure 1, conventional ring seals being present on the respective heads. At the same time, such liquid is drawn into the cylinders 39 to fill them through lines 38, 31 and 35 because valve 35 is partially opened through the pressure exerted through line 38a. as described in the aforesaid application, Serial No. 53,162.

Valve 2! is then moved to open valve is to admit low pressure water from a water line led into tube ll and the interior of pipe E8 in the testing liquid circuit. A purge valve ii is attached to head 13 and is normally open when testing bench H is open. As soon as the low pressure water from line 53a fills the testing liquid circuit and hollow body i l, water flows through opening ll in sealing head 93 and open valve All in a solid stream, generally indicating that all of the air in pipe H) has been substantially expelled, whereupon valve id is closed. At the time of the admission of low pressure water to pipe 10 valve 33 is shut off to connect the air cylinder in mechanism 32 to the exhaust port of valve 33, permitting mechanism 32 to cause pump 39 to deliver liquid through lines 43 and 35 into the sealing liquid circuit at an appropriate pro-- sealing pressure. Valve 3G is also shifted when valve 33 is shut on so that the relief at the head end of cylinders is may take place through lines ts and ll.

When the prefilling operation is completed and valve 45 is closed, valve i9 is also closed to shut off the low pressure water supply and valve 26 is opened to admit high pressure water to the test ing liquid circuit. Immediately such testing pressure is operative upon testing circuit cylinder 25, mechanism 32 and the balance of the pump control assembly to cause pump 3!} to deliver liquid through pipes dt and 35 into cylinders iii at sealing pressure. The force exerted by the sealing pressure is maintained above but very close to the testing force exerted by the testing pressure so that scaling is assured. And even thou h pipe ill foreshortens under the force of the testing pressure, the sealing force will cause sealing head E2 to creep or move forward correspondingly and maintain the sealed relationship.

When the test is over, valve 2' i closed and he L .l

valve 40 is opened to abate the pressure in the testing circuit. At the same time, valves 33' and 34 are turned to reintroduce compressed air into the air cylinder in mechanism 32 and supply liquid in the sealing liquid circuit under pressure to the piston head end of cylinders l8 through lines A l and 46. Thereby sealing head ['2 is moved away from sealing head 13 with the cylinders 39 being exhausted through line 35, valve 36 and line 38 while the opposite ends of cylinders [3 are relieved through line 45'', valve 3 4, and line 47. The pump 30' will shut oif auto matically, even though valve 33 is not turned off after test bench I l becomes fully opened, when the force exerted by springs H2 is balanced by the force resulting from pressure in line 89d against plunger 87'.

Between testing periods on test bench i a latch Hie may be swung into the position shown in Figure 2 to hold crossha'd I I i at the nonpum'ping distance from cylinderhead H 8 against the pressure of presealing control spring I32. This use of latch Mil allows the operator during such inactive periods to shut valve 33 off so that no compressed air passes into pipe" i655. During the operations of test bench H, latch l lil' is'swung' over and maintained in thed'otted position shown in Figure 3.

Pump and associated control mechanism This adjustable pressure pump 38 comprises a casing 68 rigidly bolted to a suitable foundation. Brackets 69 and iii are bolted respectively to the left and right sides of casing 68. These brackets carry arms 1! and 12, respectively, to support pump control mechanism 32. A rigid depending slideway 5b is also bolted to casing below arm 1-2 and adjustably carries a'sealing pressure cylinder assembly 5| which is a part of this invention. At the front of pump 33 there is a cover plate It and a similar suitabl cover plate Hi at the rear to enclose the pump. Threaded connection plates '55 and It are bolted by bolts l1 in concentric position about a left-hand port 18 and righthand port 19, respectively; of the pump. In the operation of pump 3%, which is of a well-known commercial type, when port "it is the intake port, port '19 is the discharge port. Conversely, when port it is the intake or suction line, port '18 isthe" discharge port.

In this type of pump, motive power is supplied through a shaft Bil j'ournaled in bearings en'- closed within the casing of the pump and not shown. Pump 36 operates in such fashion that when the working elements thereof are laterally shifted to the left, port it becomes the discharge port and when the working parts are shifted to the right, port is becomes the discharge port.

The maximum extent of any movement of the working parts to the left or right of the vertical center line through the axis of the pump is rods 8| are connected to a crosshead 82 by nuts;

33. On the right, a similar pair of guiderods 84' extend through casing 553 and areconnected' to a crosshead 85 by nuts 36. A saddle 85a is made" integral with c'rosshead 85 and spans the edge of abalance lever 98 to'which it is pivotal ly connected bya pin- 85?) passing through a short vertL cal slot 98a. There is a close fit between pin 85b and slot 98a in the plane of movement of guide rods 84. Thus, in eifect, crosshea'ds 32 and 85 are themselves rigidly connected together.

Within a pressure cylinder 93a in the lower part of bracket as, a plunger 31 is located for actuation away from the pump 36 by the introduction of oil under pressure through a line 89a and port 89 into a chamber til in cylinder 9% whenever discharge from port 18, into which pipe 89a is tapped, takes place. Plunger 8"! is located in the plane of the pair of guide rods 8| and operates parallel thereto and midway between them. Moreover, plunger 8'! abuts the inside of crosshe'ad 82. This plunger 81 is lubricated by capillary action of the actuating fluid in the sealing pressure system entering chamber 98 and working between the plunger and the bore of cylinder Sta without undue loss or leak age of oil. bore is collected in an oil-collecting chamber 93 and returned through an opening 84 to tank 2? by a suitable line.

The sealing liquid ci cuit pressure cylinder assembly 5| is adapted to slide vertically in'slide- Way and generally in a plane parallel to guide rods 84 and midway between them. Slidew'ay 53- comprises a vertical machined plane surface 52' and a pair of guide strips 5-3 on each side thereof bolted to surface 52. The outermost strip 53 is Wider than the innermost on each side and extends inwardly to form vertical grooves 54 which operate as a track in which assembly 5i slides. A carriage plate 55 is provided with side flanges 58 engaging the respective grooves 56 to retain carriage plate 55' in slidable relation against surface 52. Plate 55 is drilled at 5'! for a press fit with or other suitably firm attachment to a sealing pressure cylinder 58. A port 59 affords access to a chamber lit at the inner end of a cylinder bore 6! in a bore sleeve 6 la tightly held by a plate 61?) within cylinder 58. A flexible pressure hose 62 received liquid from the sealing liquid circuit through its connection to port 19 during discharge from port 19 to urge a piston 63 in bore 5| outwardly and horizontally. The axis of piston 63 lies within the vertical plane parallel to and midway between guide'rods 83. An oil-collecting chamber and return port may be provided for cylinder 58' on the outer end thereof corresponding to the'sam'e provision made for cylinder 96a since piston 63 is also made with a capillary fit between it and the walls of bore 5!.

Piston 63 is axially recessed at 64 on its outer end for the reception of an easy fitting stem 55 extending rearwardly of and integral with a shoe 56'. A horizontal contact her El is provided on the outermostface of shoe 56 in order to provide substantially line contact between shoe 66 and a balance lever 98. Shroud plates ill are bolted to the sides" of lever 98 to form a channel between the flanges of which shoe bar 6'! will be confined and travel during any movement thereof. Calibration markings lite may be provided on one or both shrouds 9'! so that an operator through an adjusting screw rod 8% may romptly change the vertical setting of sealing pressure cylinder assembly 5! to suit a change in the diameter of the pipe specimens being tested.

Adjusting screw rod 83 is mounted and shit ably packed for rotary but not axial movement in a bearing 9! integral with bracket 10'. A nanuwheer 92 fitting over the squared end of rod st provides for the necessary" rtiauon" thereorto Such oil as does work through the adjust pressure cylinder assembly 5% to any predetermined height. An adjustment nut :95 is bolted to carriage plate 55 and engages the threads on rod 8% so that upon turning of handwheel 92, plate 55 and assembly 5! are correspondingly raised or lowered, depending upon the direction of rotation of the handwheel. A stud bolt I01 may be threaded into the back of cylinder 5% with its stem passing through a slot Eula in slideway 50 so that turning bolt I8? to tighten it, after assembly 5| has been moved to its appropriate predetermined location, will insure the locking of assembly 5! in place prevent any inadvertent vertical movement thereof.

Lever 9B fits between the sides of saddle 85a, and is pivotally fulcrumed at 99 to bracket arm 72. The upper end of lever 38 is pivotally connected to and journaled between the sides of a clevis IQB. Clevis its is fixedly attached to a control rod III! extending inwardly thereof toward and above pump 39. The inner end of rod IIlI is shouldered and threaded as indicated at I62 for fixed engagement with a crosshead Hid. A nut Hi3 locks control rod IQI in place with relation to crosshead H54.

Crosshead its operates in a horizontal plane and at the respective outer ends thereof is engaged by a pair of spacing bolts Hid. The narrower extended ends m9 of spacing bolts Iiiii slidably pass through holes drilled through crosshead I 3 and act as spring rods slidable relative to crosshead IN. The outer ends of the spring rods I99 are threaded for the reception of loclr nuts HG. Between orosshead H9 3 and the lock nuts Hi) there are respectively located on each spring rod Its a spring retainer II I, a spring I 52 and a second spring retainer lIEi. Across the innermost ends of the spacing bolts tilt there is a crcsshead i It which is fixedly connected thereto by the nuts H5. Spacing bolts idE also freely extend through bushing lined openings H5 in arm II and openings I IT in a cylinder head I i8.

An air cylinder H9 is positioned between arm II and cylinder head H8. In air cylinder Iii",- there is a piston I26 and a fibrous piston facing disc 52!. A piston rod I22 has a stud shoulder portion 23 the inner end of which is threaded into a piston follower I24 to connect piston rod I22 to piston I20. Piston rod I22 extends through a bushing I25 in cylinder head E58 and abuts against the inner, that is the right side as shown in Figure 2, of crosshead IE I. Cylinder lie is single acting and operates by compressed air entering the cylinder through port i2$ when air valve 33 is turned to admit compressed air into line I35. Extending outwardly of crosshead II intermediate the ends thereof is a stud shaft I23, the inner end of which is threaded for engagement with the crosshead i Id and for engagement with adjusting nuts I28.

Synchronization cylinder 26 has a piston filo therein which is coaxial with and normally abuts the outer end of stud shaft I27. Cylinder 26 is maintained in position relative to the pump control mechanism 32 by spacing bolts E36 respectively threaded into cylinder head H8 at their inner ends. Cylinder head IIB in turn is maintained in position relative arm II by the bolts I3 I.

A packing gland I33 using conventional packing is bolted to cylinder 26 and prevents leakage of the high pressure testing fluid around plunger 51a. Between the packing gland I33 and the adjusting nuts I28, a spring I32 is positioned at the respective ends of which suitable retainers I 34 and I35 are provided. Hence, by means of adjusting nuts I28 the loading of spring I32 can be varied for the purpose of effectively and automatically presealing the test specimen with the correct amount of presealing force during the prefilling stage of the testing cycle.

Operation of pump control assembly In initiating a new testing cycle, valve 33 is turned to admit compressed air into line H and thence into air cylinder II9 through port I26. Thereby, guide rods 8| are moved to the right as viewed in Figure 2 causing discharge from port in to close test bench II through the proper setting of valve 35 against a newly positioned pipe rength I0. This closing of test bench II is under the control of springs IIZ which are set at an appropriate back pressure to insure closure without any crushing of pipe I0. Thus, even if the operator should fail to shut valve 33 off at the moment of achieving the proper closure relation between test bench II and pipe I8, no damage is done because when the hydraulic liquid in the sealing pressure system attains a predetermined pressure, the force exerted thereby on plunger 8'! will restore pump 30 to neutral, non-pumping position by the pull exerted through lever 98, rod Iiil, crosshead we and spring retainers H3 on the springs H2.

With the test bench II closed on a pipe Iii, valve 33 is then turned to shut-ofi position and relieves cylinder IIS through port I26, line I35 and exhaust line MI. Thereupon, spring I32 assumes control for presealing pushing crosshead H t, and thereby control rod IIII, to the right as shown in Figure 2. This causes a corresponding movement of guide rods 84 to the left, initiating discharge from port I9 of pump 38. The pressure of such discharge will be controlled by the compression of spring I32 by the adjusting nuts I28. Thereby the presealing force exerted by the pressure of the sealing circuit liquid against plungers I6 will be determined by spring I32 during the prefilling of pipe II with water admitted into valve I9 from line I9a.

When the hollow body undergoing test is filled with water and valve is closed, the apparatus is ready for the application of full testing and sealing pressures and forces. It is at this juncture of the testing cycle that the sensitive relation of sealing force to testing force must be obtained particularly with thinner walled specimens or those whose length increases the slenderness ratio to the point where unbalanced sealing and testing forces may either crush or bow or damage the test specimen. While the sealing force is always to be maintained greater than the testing force, the difference between such forces must be held within narrow limits during the increase in each thereof from the starting forces to the maximum effective in the particular testing cycle. It is the close correlation of the two forces during the pressure testing stage of the testing cycle that is sensitively obtained by and especially important in the system of this invention.

At the present time, testing pressure exerted by the liquid, usually water, in the testing pressure system at the testing stage may run as high 12,099 lbs. per square inch. On the other hand, the pressure of the liquid in the sealing liquid system, which pressure is derived from pump as as a pressure source, may remain at a much lower figure such as, for example, 2500 lbs. per square inch, maximum sealing pressure. The sealing and testing forces, corresponding to the area over which such pressures are respectively applied multiplied by such pressures respectively, may, however, be placed in sealing balance by the practice of this invention regardless of changes in the sizes of the hollow bodies undergoing test and regardless of the close margin afforded the operator by the respective column strengths thereof.

In the testing stage of the testing cycle in the preferred embodiment of this invention, liquid at the sealing or delivery pressure at port it passes through line 02 and urges piston 63 against lever 85 through the horizontal line con tact aiforded by bar 51'. This actuation tends to return lever to its vertical, that is, its neutral or non-pumping position. The force exerted by piston 03 is rigidly opposed by control rod 3558 bly i! which is directly and rigidly acted upon by piston 67a in cylinder 1%. Because of the characteristics of pump iii the movements of pieton file reflecting a change in the pressure of the testing liquid in the testing circuit are immediately reflected by corresponding change in the rate or build-up of sealing pressure of the liquid discharged from port is and vice versa. The proportion of the cross sectional areas of the respective pistons 63 and i'ila, taken together with the characteristics of the respective pressure sources for the respective liquids in the independent sealing and testing circuits are such that in the testing stage of the testing cycle the testing force against sealing head I2 to open it cannot exceed the sealing force exerted on the cross sectional areas of the plungers !6. Conversely, such sealing force cannot so outrun the testing force as to give rise to the risk of crushing or bowing the pipe l0.

Such continual and close correlation and balance between sealing and testing forces is obtained by the predetermined positioning of sealing pressure cylinder assembly 5!, for a given diameter of pipe lengths i0 to be tested, along the slideway 50 so that under the effect of the pre determined testing pressure to be applied to specimens of that diameter the respective moments of force exerted on lever 98 to rotate it about its fulcrum 99 act and will remain in sealing balance throughout the testing stage at high pressure. When the internal diameter of the hollow bodies are changed, it is a simple task, even in continuous production testing, to loosen bolt I01 and turn handwheel 92 to shift assembly 5| to a new predetermined sealing balance position using the calibration markings I06.

Thus, by way of example and not by way of limitation, the following illustrations will show the magnitude of some of the respective testing and sealing forces which may be kept in proper and continuous balance by the practice of this invention:

Example 1.-In testing a 7-inch outside diameter steel pipe having a cross sectional area of 38 sq. in. to 5000 lbs. per sq. in. internal pressure, the pipe being sealed on its outside diameter, a total testing force of 192,500 lbs. is developed tending to separate sealing heads l2 and 13. On the basis that plungers 16 each have a cross sectional area of 55 sq. in., the sealing pressure required will be 1750 lbs. per sq. in. If plunger 67a has a cross sectional area of 1 sq. in., it will exert a force of 5000 lbs. against rod l 0| under the applied test pressure of 5000 lbs. per sq. in. If plunger 63 has a cross sectional area Of 2 sq. in., it develops a force of 3500 lbs. under the sealing pressure of 1750 lbs. per sq. in.

10 required. Therefore, to balance the sealing force against the testing force, if the distance from clevis to pivot '99 is 4 inches, plunger 03 must be placed so as to act against lever 03 a distance of 5.72 inches from pivot 90.

Example 2.-On the basis of specimen and dimensions set forth in Example 1 but when applying a test pressure 3000 lbs. per sq. in. internal pressure, a testing force is developed of 115,500 lbs, tending to separate sealing heads l2 and it. The balancing sealing pressure must therefore be 10% lbs Plunger 51a exerts a force of lbs. under the conditions of this Example 2 and plunger 53 exerts a force of 2090 lbs. Therefore, plunger 53 must remain at 5.72 inches from pivot thereby illustrating that in the practice of this invention no new setting of assembly 5| is required for changes in the full testin pressure to be applied.

Example 3.-In testing a pipe of 4 inches outside diameter having a cross sectional area of 16 sq. in., and on the basis of the same test bench apparatus dimensions set forth in Example 1, plunger 63 must be reset for any applied testing pressure to a distance along lever 03 13% inches distant from pivot 00.

It is evident that various modifications in the proportions of the parts and in their positioning and in the characteristics of the respective pressure sources and in the liquid circuits may be made without departing from the spirit of this invention or the scope of the appended claims.

I claim:

1. In a system for hydrostatically testing hollow bodies and having independent sealing liquid and testing liquid circuits with a pressure source for each of said circuits, displacement means acted upon by the pressure in said sealing liquid circuit, displacement means acted upon by the pressure in said testing liquid circuit and engaging said first-mentioned displacement means, lever means engaged by said displacement means at respective distances along said lever means for balancing the respective forces exerted by said respective displacement means, and means for varying the distance along said lever means of at least one of said displacement means, whereby the sealing force exerted by the pressure in said sealing liquid circuit is maintained in close sealing balance with the testing force exerted by the pressure in said testing liquid circuit.

2. In a system for hydrostatically testing hollow bodies having sealing pressure and testing pressure circuits, lever means having a fulcrum, means responsive to sealing pressure bearing against said lever means a predetermined distance from said fulcrum and adapted to turn said lever means thereabout in one direction, means responsive to testing pressure bearing against said lever means a predetermined distance from said fulcrum and adapted to turn said lever means thereabout in a direction counter to said first-mentioned direction, and means to vary the distance of at least one of said bearing means from said fulcrum, whereby the sealing force exerted by said sealing pressure may be maintained in closely correlated and balanced synchronism with the testing force exerted by said testing pressure.

3. In a system for hydrostatically testing hollow bodies employing a conventional hydraulic sealing pressure pump, sealing pressure means for returning said pump when pumping to a neutral non-pumping position when sealing pressure is attained, testing pressure means opposing such return, and lever mechanism connecting said respective means'in adjustable relation to at least one of said means by varying the distance of said last'mentioned means along said lever mechanism, whereby the force exerted by said testing pressure means is adapted to be sensitively and continuously balanced by the force exerted by said sealing pressure means.

4. In a system having sealing and testing liquid circuits for hydrostatically testing hollow bodies, pressure sources for the liquids in said circuits, displacement members respectively acted upon by said sources, said displacement members being in rigid engagement opposed to each other, and means respectively engaged by said displacement members to move them in relation to one another to maintain said system in balanced sealing relation between the sealing and testing forces exerted by said pressure sources.

5. In a system for hydrostatically testing hollow bodies and having independent sealing liquid and testing liquid circuits with a pressure source for each of said circuits, piston means acted upon by the pressure in said sealing liquid circuit, piston means acted upon by the pressure in said testing liquid circuit and engaging said firstmentioned piston means in an opposed manner, means for changing the pressure of at least one of said pressure sources to balance the respective forces exerted by said respective piston means, and means for shifting at least one of said piston means relative to the other and in a non-axial direction relative to itself, whereby the sealing force exerted by the pressure in said sealing liquid circuit is adapted to be maintained in close sealing balance with the counteracting testing force exerted by the pressure in said testing liquid circuit for diiferent sizes of such hollow bodies.

6. In a system for hydrostatically testing hollow bodies employing a conventional hydraulic sealing pressure pump, sealing pressure means for returning said pump when pumping to a neutral non-pumping position when sealing pressure is attained, testing pressure means in engagement with said sealing pressure means to oppose such return, lever means engaging said pump and adapted by its movement to vary the pressure thereof, said lever means connecting said respective pressure means about a fulcrum, and means for adjusting the leverage ratio between said means measured from said fulcrum, whereby the force exerted by said sealing pressure means is adapted to be sensitively and continuously kept in balance about the fulcrum of said lever means with the force exerted by said testing pressure means for diiferent sizes of such hollow bodies.

'7. In a system for hydrostatically testing hollow bodies having sealing pressure and testing pressure circuits, at least one of said circuits having a variable pressure source, lever means engaging said pressure source and adapted by its movement to vary the pressure of said pressure source, said lever means having a fulcrum, means responsive to scaling pressure bearing against said lever means a predetermined distance from said fulcrum and adapted to turn said lever means thereabout in one direction, means responsive to testing pressure bearing against said lever means a predetermined distance from said fulcrum and adapted to turn said lever means thereabout in a direction counter to said firstmentioned direction, and means for relatively adjusting said pressure responsive means to change the respective ratio between said predetermined distances to compensate for a change in the cross sectional area of the hollow bodies being tested, whereby by the balancing of said two first-mentioned means about said fulcrum the sealing force exerted by said sealing pressure may be maintained in close correlated synchronism with the testing force exerted by said testing pressure.

8. In a system for hydrostatically testing hollow bodies having independent sealing liquid and testing liquid circuits, a hydraulic pum adapted to act as a pressure source for said sealing liquid circuit, a working member in said pump adapted to be movable between a neutral non-pumping position and a full volume discharge position, a lever pivotally connected to said working memher, said lever having a fixed fulcrum relative to said pump, a control rod assembly pivotally connected to said lever, a testing circuit piston in said testing liquid circuit adapted to be acted upon by the pressure in said testing liquid cir cuit, said control rod assembly being in direct thrust engagement with said testing circuit piston, a pressure cylinder assembly in said sealing liquid circuit, a piston in said pressure cylinder assembly adapted to bear against said lever and exert a moment of force about said fulcrum counter to the moment of force about said fulcrum exerted by said testing circuit piston through said control rod assembly, said pressure cylinder assembly being positioned at a predetermined distance from said fulcrum, whereby the sealing force during testing in said system is sensitively and continuously maintained in sealing balance relative to the testing force in said system.

9. In a system having sealing and testing oircuits for hydrostatically testing hollow bodies, a

hydraulic pump adapted to act as a pressure source for said sealing circuit, a working memher in said pump adapted to be movable between a neutral non-pumping position and a full volume discharge position, a lever pivoted adjacent to said pump and engaged by said working member, a pressure cylinder positioned adjacent said pump and adapted to be actuated by the discharge therefrom, a piston in said pressure cylinder rigidly engaging said lever in such a manner as to tend to move said working member into neutral non-pumping position, a second pressure cylinder in said system adapted to be actuated by the pressure in said testing circuit, a second piston in said second pressure cylinder rigidly engaging said lever in a manner as to tend to move said working member into full volume discharge position, and means for balancing the forces respectively exerted by said pistons, whereby the sealing force against a hollow body during the operation of said system is adapted to increase in synchronism with the testing force to effect sealing and take-up caused by any foreshortening of said hollow body without impairing the strength of said hollow body.

10. In a system for hydrostatically testing hollow bodies on a test bench having relatively movable heads, a sealing pressure pump having variable and reversible discharge, resilient means controlling one of the discharges from said pump for opening and closing said test bench, a second resilient means for controlling another discharge from said pump for presealing said testing bench against a hollow body to be tested, a testing pressure pressure source, a plunger in said testing pressure pressure source in rigid engagement with said pump to cause said pump to discharge at sealing pressure, a second plunger acted upon by said sealing pressure in rigid engagement with said first-named plunger to oppose the force exerted by said first-named plunger on said pump, a balance lever acted upon by said respective plungers in said engagement, and means for shifting at least one of said plungers relative to said balance lever to equalize the forces exerted by said respective plungers, whereby for different cross sectional areas of pipe tested on said test bench, the sealing force exerted between the heads of said test bench may be maintained in sealing balance without oversealing relative to the testing force exerted by the testing pressure within said hollow body.

11. An apparatus of the class described comprising a fluid pressure mechanism, a seal actuated by said mechanism for sealing a hollow article to be tested, a source of pressure fluid con- 14 nected to the interior of said article, a variable delivery pump delivering hydraulic fluid to the mechanism for actuation thereof, a device operatively connected to the pump for varying the delivery of said pump, and another device connected to said source and operated by the pressure therefrom through a relatively incompressible connection to control the first-mentioned device, for automatically increasing the pressure of hydraulic fluid delivered by said pump in direct proportion to increase of pressure in said article by fluid from said source.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,326,345 Ernst et al Aug. 10, 1943 2,329,035 Cross Sept. 7, 1943 2,520,856 Schowalter Aug. 29, 1950 2,522,927 Camerota Sept. 19, 1950 

